Emeralds-garnets-tourmaline in pegmatitic granite (Crabtree Pegmatite, Devonian; Crabtree Mountain, Mitchell County, North Carolina, USA) 3 : 無料・フリー素材/写真
Emeralds-garnets-tourmaline in pegmatitic granite (Crabtree Pegmatite, Devonian; Crabtree Mountain, Mitchell County, North Carolina, USA) 3 / James St. John
| ライセンス | クリエイティブ・コモンズ 表示 2.1 |
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| 説明 | Pegmatite from the Devonian of North Carolina, USA.Pegmatites are intrusive igneous rocks consisting of very large crystals (defined as >1 centimeter). They can form by very slow cooling of magma or cooling of a water-rich magma. Most pegmatites form by the latter.The rock shown here is from North Carolina's famous Crabtree Pegmatite, which produces emeralds (= green specks). In this shot, the elongated and subtriangular, black crystals are schorl tourmaline (a complex silicate), the pinkish-reddish crystals are garnet, the medium-gray glassy material is quartz (SiO2 - silica), and the whitish-gray is feldspar.This is one of many pegmatites that have intruded metamorphic rocks of the Precambrian-aged Ashe Formation.Geologic unit: Crabtree Pegmatite, Spruce Pine Plutonic Suite, Gossan Lead Thrust Block, eastern Blue Ridge Mountains, Devonian, ~377 to 404 MaLocality: subsurface mine at Crabtree Mountain, ~2.5 km northwest of Little Switzerland & ~7.5 km southwest of Spruce Pine, Spruce Pine District, southern Mitchell County, western North Carolina, USA (~35° 52' 30" North latitude, ~82° 07' 20" West longitude) |
| 撮影日 | 2017-12-11 11:40:44 |
| 撮影者 | James St. John |
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